Dengue viruses can cause dengue fever and the more severe disease, dengue hemorrhagic fever/shock syndrome (DHF/DSS). Infection with dengue viruses is the leading cause of hospitalization and death in children in at least 8 tropical Asian countries. There are 4 types of dengue virus (DENV-1, DENV-2, DENV-3, and DENV-4), each of which can cause dengue illness ranging from a mild illness to life-threatening disease. This study will evaluate the experimental rDEN2Δ30-7169 vaccine for the prevention of illness due to DENV-2. The purpose of this study is to evaluate the safety and immunogenicity of this vaccine in healthy adults with no history of previous flavivirus infection.